Macromolecular mediator catalyst, composite positive electrode material and application of composite positive electrode material

Abstract

The invention discloses a high-molecular mediator catalyst, a composite positive electrode material and application of the composite positive electrode material. The high-molecular mediator catalyst is prepared from an organic micromolecular monomer with oxidation-reduction activity through a chemical or electrochemical polymerization method. A composite positive electrode material of a rechargeable metal-air battery or a lithium-sulfur battery is composed of the polymer mediator catalyst, a carbon material and a binder. The high-molecular mediator is formed by polymerizing organic micromolecular monomers through a chemical or electrochemical method, has a multifunctional catalytic characteristic, and is compounded with a high-pore carbon material to form a composite positive electrode material with a synergistic effect, so that the charge-discharge efficiency, the capacity and the cycle stability of a battery are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a polymer mediator catalyst, a composite positive electrode material and applications thereof. Background Art

[0002] Batteries initially powered small devices such as remote controls and watches, but now also have important applications in consumer electronics, electric vehicles, and the military. This rapid development has posed new challenges to battery technology. The dominant lithium-ion battery has a low energy density (no more than 400Wh·kg) due to the inherent theoretical capacity limitations of the electrode material. -1 ), which limits the driving range of electric vehicles. Therefore, it is urgent to find a battery system with higher energy density.

[0003] With ultra-high theoretical energy density (≈3500Wh·kg -1 )'s Li-O2 battery has attracted much attention. Li-O2 batteries consist of three main parts: Li anode, air cathode, and electrolyte. The battery reaction is The forward direction represents discharge, which is an oxygen reduction process (ORR Oxygen Reduction Reaction). The reverse direction represents charge, which is an oxygen evolution process (OER Oxygen Evolution Reaction). However, such a simple electrochemical process faces many challenges. These challenges are mainly related to the oxygen reaction at the air cathode of the lithium-oxygen battery. For example, the discharge product Li2O2 is an insulator with a large band gap (~4.9eV), which usually hinders electron transfer and ion diffusion, resulting in slow oxygen electrochemical kinetics. Moreover, the reaction potential of Li2O2 decomposition is high, making it difficult for the reaction to occur during charging, and the decomposition is often incomplete, thereby limiting the cyclability and stability of the battery. In addition, O2 generated by oxygen electrochemistry - , LiO2 and 1 O2 is highly reactive and easily reacts with electrolyte and cathode components to form Li2CO3 and LiOH. These challenges lead to lithium-air batteries often suffering from poor reversibility, low capacity, low current density and poor cyclability, making their commercialization difficult.

[0004] The use of catalysts can effectively regulate battery performance, increase charge and discharge capacity and current density, and accelerate the practical application of lithium-air batteries. The working principle of catalysts is as follows: (1) regulating the formation pathway and deposition behavior of Li2O2 during the ORR process to accelerate the electrochemical reaction kinetics, thereby increasing the current density and battery capacity; (2) regulating the decomposition pathway of Li2O2 during the OER process to reduce the overpotential during charging, thereby improving the cycle stability of the battery.

[0005] Traditional catalysts include soluble redox mediators (RMs), precious metals, and transition metal oxides. Transition metal oxides have limited catalytic performance. While soluble RMs can reduce the overpotential during discharge and increase battery capacity to a certain extent, they can also travel from the cathode to the lithium anode and decompose there, leading to severe degradation of the lithium anode and functional degradation of the media. While precious metal catalysts offer significant catalytic effects, their high cost makes them unsuitable for practical application. Summary of the Invention

[0006] To address the deficiencies of the prior art, the present invention aims to provide a polymer mediator catalyst, a composite cathode material, and applications thereof. The polymer mediator is a soluble redox mediator prepared by chemical or electrochemical polymerization. The modified carbon cathode has a multifunctional catalytic effect, which can catalyze the generation and decomposition of discharge products of rechargeable metal-air batteries or lithium-sulfur batteries, improve battery reaction kinetics, increase battery capacity, and effectively inhibit the "shuttle effect", thereby improving battery life and cycle stability.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A high molecular mediator catalyst is prepared by chemical or electrochemical polymerization of organic small molecule monomers with redox activity.

[0009] Preferably, the polymerization method of the aforementioned polymer mediator catalyst is in situ or ex situ polymerization, and the organic small molecule monomer is selected from the redox mediator of metal-air batteries or lithium-sulfur batteries, and is one or more of organic small molecule nitrides, organic small molecule sulfides, quinones, and heteropoly acids.

[0010] Application of polymer-mediated catalysts in the preparation of cathode materials for rechargeable metal-air batteries or lithium-sulfur batteries.

[0011] A composite positive electrode material for a rechargeable metal-air battery or a lithium-sulfur battery is composed of the above-mentioned polymer mediator catalyst, a carbon material and a binder.

[0012] Preferably, the mass ratio of the aforementioned polymer mediator catalyst, carbon material and binder is (20-30): (55-70): (8-12).

[0013] Preferably, the aforementioned carbon material is one or more of multi-walled / single-arm carbon nanotubes, carbon nanofibers, graphene, acetylene black, Ketjen black, Super P, ordinary carbon black, conductive graphite, biowaste-derived carbon, metal-organic framework-derived carbon, carbon-based composite materials or biochar materials.

[0014] Preferably, the aforementioned metal-air battery is one of a Li-O2 / CO2 battery, a Na-O2 / CO2 battery, a K-O2 / CO2 battery, a Mg-O2 / CO2 battery or a Zn-O2 / CO2 battery.

[0015] Preferably, the aforementioned positive electrode material has a multi-level pore structure, including micropores, mesopores and macropores, with a pore diameter of 0.5-200 nm.

[0016] Preferably, the aforementioned positive electrode material further comprises transition metal nanoparticles, and the transition metal is selected from one or more of Fe, Co, Ni, and Mn.

[0017] The present invention is beneficial in that:

[0018] (1) The core of the design of the polymer mediator of the present invention lies in the controllability and functionalization of the molecular structure. By selecting organic small molecule monomers with specific functional groups and combining them with chemical or electrochemical polymerization methods, the directional introduction and spatial distribution optimization of catalytic active sites can be achieved. The main chain or side chain of the polymer mediator is introduced with redox active groups such as quinones, nitroxide free radicals, and sulfides, which endow it with efficient electron transfer ability. These groups directly participate in the catalytic cycle during the battery charging and discharging process through reversible redox reactions, thereby reducing the reaction energy barrier.

[0019] (2) The carbon positive electrode modified with polymer catalyst has a dual-functional catalytic effect. Some polymers can simultaneously catalyze the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in metal-air batteries, reduce the charge and discharge overpotential, and promote the uniform deposition and efficient decomposition of discharge products (such as Li2O2, Na2O2); by physically adsorbing or chemically bonding to fix RM or polysulfide, inhibiting RM from shuttling to the negative electrode and decomposing, it can also significantly reduce the dissolution and diffusion of polysulfide in lithium-sulfur batteries and improve the capacity retention rate; polymer-carbon composite materials with hierarchical pore structure can increase the oxygen diffusion coefficient by 40%-50%, and regulate the oxygen adsorption / desorption kinetics, thereby improving the rate performance of metal-air batteries; by replacing precious metal catalysts and utilizing biowaste-derived carbon materials, the manufacturing cost can be greatly reduced, while reducing dependence on scarce resources; and it can reduce or avoid the possibility of the existence of unstable intermediates in metal-air batteries or reduce their existence time, thereby improving reaction stability;

[0020] (3) The polymer catalyst of the present invention can be compounded with transition metal nanoparticles to form a synergistic catalytic system. The molecular design of the polymer can also regulate the electron transfer path, enhance the electrode conductivity, and thus improve the utilization rate of the sulfur positive electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1is the redox diagram of PTEO itself in Example 1 of the present invention;

[0022] Figure 2 This is the LSV diagram of commercial Li2O2 oxidized by PTEO in Example 1 of the present invention;

[0023] Figure 3 1 is the charge-discharge curve of the positive electrode containing PTEO in Example 1 of the present invention;

[0024] Figure 4 is a potential scan diagram of AQD in Example 2 of the present invention;

[0025] Figure 5 This is a 0.2 mA / mg constant current discharge diagram of a lithium-oxygen battery using a coated PAQ electrode as a positive electrode in Example 2 of the present invention;

[0026] Figure 6 CV graph of the PTEO-PAQ-CNT positive electrode sheet in Example 3 of the present invention;

[0027] Figure 7 1 is a full charge and discharge diagram and a comparison diagram of the lithium-oxygen battery containing the PTEO-PAQ-CNT positive electrode sheet in Example 3 of the present invention;

[0028] Figure 8 It is a cycle comparison chart of the batteries prepared in Example 3, Comparative Example 1 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] A method for preparing a composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery is as follows:

[0032] (1) Synthesis of polymer mediator catalyst by chemical method: Under Ar atmosphere, a mixture of 0.50 g of 4-glyceryloxy-2,2,6,6-tetramethylpiperidin-1-oxyl (GTEMPO, 2.2 mmol), 0.05 g of carbon nanotubes (CNTs) and 10 mg of potassium tert-butoxide (0.09 mmol) was heated at 80°C for 5 hours. After cooling to room temperature, dichloromethane was added to the reaction mixture, and the organic solution was washed with water. The organic layer was poured into n-hexane to produce a viscous liquid. The viscous liquid was decanted to obtain a crude polymer product. The crude polymer product was dissolved in a small amount of tetrahydrofuran, and the polymer was precipitated in n-hexane again. The obtained polymer was then dried in vacuum at room temperature overnight to obtain the polymer poly-4-epoxy-2,2,6,6-tetramethylpiperidin-1-oxyl (PTEO).

[0033] (2) Preparation of positive electrode material: PTEO: CNT: polytetrafluoroethylene (PTFE) = 2:7:1 was coated on a stainless steel mesh and vacuum dried at 120°C for 12 hours to obtain a PTEO-CNT positive electrode material. The loading amount was 1 mg / cm 2 .

[0034] Example 2

[0035] A method for preparing a composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery is as follows:

[0036] (1) Preparation of monomeric AQD: 1-Aminoanthraquinone (200 mg) and HCl (36%, 2.5 mL) were added to H2O (1 mL) and stirred in an ice bath for approximately 30 min. Then, 10 mL of H2O containing NaNO2 (90 mg) was added dropwise to the mixture. Finally, 10 mL of H2O containing NaBF4 (115 mg) was added to the mixture. The product precipitated at the bottom of the solution. The precipitate was collected by filtration, washed thoroughly with cold water and ether, and finally dried under vacuum and stored at 0°C to obtain monomeric AQD.

[0037] (2) Preparation of electrode sheets: CNT and polyvinylidene fluoride (PVDF) were mixed and ground evenly in a mass ratio of 8:1, and then slurried with tetrahydrofuran (THF). The slurry was applied on a stainless steel mesh with a diameter of 12 mm and dried at 60°C to form electrode sheets. The loading of each electrode sheet was 1 mg / cm 2 .

[0038] (3) Synthesis of conductive polymer by electrochemical method: Using the electrode sheet of step 2 of this example as the working electrode, a platinum sheet (1 cm × 1 cm) as the counter electrode, and AgCl / Ag as the reference electrode, cyclic voltammetry (1.7-3.8 V vs. Li) was performed in an acetonitrile electrolyte containing 2 mM AQD and 0.1 M tetrabutylammonium perchlorate (TBAP). + / Li, 10 mV / s, 3 cycles) for electrochemical grafting, and the PAQ-CNT positive electrode material was obtained after rinsing with ethanol.

[0039] Example 3

[0040] A method for preparing a composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery is as follows:

[0041] The PAQ-coated carbon electrode in Example 2 was ultrasonically removed, and the PAQ-coated carbon was ultrasonically removed. The slurry was prepared with PTEO, CNT, and PTFE prepared in Example 1 in a mass ratio of 5:2:2:1 and coated on a stainless steel mesh. The slurry was dried at 120°C for 12 hours and then used to obtain a PTEO-PAQ-CNT positive electrode material.

[0042] Example 4

[0043] Using polypyrrole (PPy) as a polymer catalyst, the catalytic material was constructed by in-situ oxidative polymerization with Fe3O4 nanoparticles, and SiO2 microsphere templates were introduced to regulate the pore structure. The specific steps are as follows: pyrrole monomer (0.5g) was dissolved in a mixed solution of ethanol and deionized water with a volume ratio of 3:1, and pre-ultrasonic dispersed Fe3O4 nanoparticles (mass fraction 10%), Ketjen Black conductive carbon (1g) and SiO2 microsphere templates (particle size of about 50nm, mass fraction 10%) were added. Under ice-water bath conditions, FeCl3 solution (0.1mol·L -1 ) as an oxidant and stirred at room temperature for 12 hours to form a PPy@Fe3O4@KB@SiO2 composite. The resulting product was filtered and washed. The SiO2 template was then etched with a 1 mol / L NaOH solution at room temperature for 3 hours, washed until neutral, and dried to obtain a Fe3O4@PPy@KB composite with a hierarchical pore structure.

[0044] Comparative Example 1

[0045] Preparation of electrode sheets: CNT and PTFE were mixed and ground evenly in a mass ratio of 8:1, and then made into a slurry with ethanol, applied on a stainless steel mesh, and dried at 120°C to make an electrode sheet.

[0046] Comparative Example 2

[0047] Electrode preparation: A slurry of AQ, TEMPO, CNT, and PTFE in a mass ratio of 2:2:5:1 was coated onto a stainless steel mesh and dried at 120°C for 12 hours before use. This produced the TEMPO-AQ-CNT cathode material. TEMPO is an organic small-molecule monomer of unpolymerized PTEO, and AQ is an organic small-molecule monomer of unpolymerized PAQ.

[0048] Comparative Example 3

[0049] Sublimed sulfur and conductive carbon black (Super P) were mixed in a mass ratio of 7:3 and heat-treated at 155°C in vacuum for 12 hours to obtain a sulfur-carbon composite with a sulfur content of 70.3±0.5wt% (verified by TGA, N2 / 10°C / min). The composite was ball-milled in NMP (300 rpm) for 4 hours with Super P and PVDF in a mass ratio of 8:1:1, coated on 15μm aluminum foil, dried in vacuum at 120°C for 12 hours, and rolled to a thickness of 80±5μm (sulfur surface loading 2.0±0.1mg / cm 2). CR2032 batteries were assembled in an argon glove box (H2O / O2<0.1ppm): lithium sheet anode / Celgard 2325 separator / 30μL electrolyte (1M LiTFSI in DOL:DME=1:1v / v+2wt%LiNO3).

[0050] Performance testing

[0051] (1) The PTEO-CNT material prepared in Example 1 was used as the positive electrode, metal Li was used as the negative electrode, and 1M LiTFSI 4G was used as the electrolyte to form a button cell. CV was scanned at a scan rate of 5 mV / S. Figure 1 As shown, the redox peak of PTEO itself was obtained.

[0052] Commercial lithium peroxide (Li2O2, Alfa Aesar, 99.5%), PTEO, and PVDF binder were mixed in a mass ratio of 4:4:2, NMP solvent was added, and ball milling was performed for 6 hours (300 rpm) to prepare a uniform slurry. The slurry was coated on a stainless steel mesh current collector with a diameter of 12 mm and vacuum dried at 120°C for 12 hours to obtain a positive electrode sheet (Li2O2 loading 2.6±0.1 mg / cm 2 PTEO loading 1.1±0.05mg / cm 2 ).

[0053] The electrode sheet was used as the positive electrode, a metal lithium sheet (12 mm in diameter, 200 μm in thickness) as the negative electrode, 1 M LiTFSI 4G as the electrolyte, and Celgard 2325 as the separator to assemble a CR2032 button cell. Linear sweep voltammetry (LSV) was used. Figure 2 As shown, the test was performed on an electrochemical workstation (CHI760E) at a scan rate of 0.1 mV / s and a voltage range of 2.0-4.5 V (vs. Li / Li+). By integrating the current-time relationship (Q=∫I dt) of the LSV curve, an electrode capacity of 3 mAh / mg was calculated, and the decomposition potential of Li2O2 during charging was 3.8 V vs. Li + / Li. This indicates that PTEO modification effectively improves the redox activity of Li2O2.

[0054] The lithium-oxygen battery assembled with the PTEO-CNT composite material as the positive electrode, metallic lithium as the negative electrode, and 1M LiTFSI 4G as the electrolyte exhibited a low charging platform of 3.7V at a current density of 0.1mA / mg (0.5V lower than that of the conventional positive electrode) and a 100-cycle capacity retention rate of 82%, confirming that PTEO modification can significantly improve the redox reversibility of the battery. The PTEO-CNT material prepared in Example 1 was used as the positive electrode, metallic Li as the negative electrode, and 1M LiTFSI 4G as the electrolyte. The charge-discharge curve of the lithium-oxygen battery containing the PTEO positive electrode was obtained, as shown in FIG. Figure 3 As shown, the battery charging platform is 3.7V.

[0055] (2) The PAQ-CNT electrode prepared in Example 2 was used as the positive electrode, metallic lithium was used as the negative electrode, and 1M LiTFSI 4G was used as the electrolyte to assemble a CR2032 type lithium oxygen battery. Figure 4 As shown in the figure, the deposition peak of PAQ and its own redox peak on the positive electrode sheet were obtained. After rinsing with ethanol, the PAQ-CNT positive electrode sheet was obtained. By integrating the redox peak charge at 2.1V in the CV curve and calculating the mass of PAQ active material according to Faraday's law, the PAQ loading per electrode sheet was obtained to be 0.3mg / cm 2 The total loading of each electrode sheet is 1.3 mg / cm 2 In an oxygen atmosphere (O2 pressure of 1.05 atm), the battery was discharged at a constant current density of 0.5 mA / mg, and the cut-off voltage was 2.0 V vs. Li + / Li. At the same time, the positive electrode sheet prepared in Comparative Example 1 was discharged at a constant current under the same conditions. Figure 5 As shown in the figure, the battery containing the PAQ-coated positive electrode has a higher discharge capacity and a lower overpotential, indicating that compared with the comparative example, the mediator PAQ can catalyze the formation of Li2O2 and improve the discharge capacity of the battery.

[0056] (3) The PTEO-PAQ-CNT composite material prepared in Example 3 was used as the positive electrode, metal Li was used as the negative electrode, and 1M LiTFSI4G was used as the electrolyte. CV was performed on a button cell (scan rate was 20 mV / s). Figure 6 As shown in Figure 2, the redox peaks of PTEO and PAQ were obtained. The PAQ loading was calculated to be 0.31 mg / cm by integrating the charge of the redox peak of PAQ at 2.1 V and the redox peak of PTEO at 3.8 V. 2 , the PTEO loading is 0.37 mg / cm 2 The total loading of the electrode sheet is 1.68 mg / cm 2 .

[0057] The electrodes in Example 3 and Comparative Example 1 were used as positive electrodes, metal Li as negative electrodes, and 1M LiTFSI 4G as electrolyte to prepare lithium-oxygen batteries. 2 Full charge and discharge test is carried out at a current density of Figure 7 As shown, the capacity of the battery prepared in Example 3 is 14.3 mAh / mg, and the overpotential is 0.8 V. The capacity of the battery prepared in Comparative Example 1 is 5.3 mA / mg, and the overpotential is 1.6 mA / mg. Compared with Comparative Example 1, the PTEO-PAQ-CNT composite material exhibits a larger capacity and a lower overpotential.

[0058] The batteries prepared in Example 3, Comparative Example 1 and Comparative Example 2 were cycled at a current density of 1 mA / mg. Figure 8 As shown, the battery prepared in Comparative Example 1 died after only 8 cycles, indicating poor cycling performance, while the battery prepared in Example 3 remained operational after 100 cycles. Compared to Comparative Example 2, under otherwise identical cycling conditions, the PTEO-PAQ-CNT cathode, due to its immobilization on the positive electrode, inhibited the shuttling of redox mediator molecules, while its unpolymerized organic small molecules (TEMPO for PTEO and AQ for PAQ) died in less than one cycle due to the shuttling effect. The battery in Comparative Example 3 was tested at 25°C: after 100 cycles at a rate of 0.5C, the capacity retention was only 58±3%, and the coulombic efficiency fluctuated by more than 12%, demonstrating significant capacity fading and polysulfide shuttling.

[0059] (4) The PTEO-PAQ-CNT composite cathode material provided by the present invention exhibits excellent electrochemical performance in lithium-oxygen batteries through the synergistic catalysis of dual mediators. Experimental data show that the composite cathode has a high electrochemical performance at 0.1 mA / cm 2 A high discharge capacity of 14.3 mAh / mg can be achieved at a current density of 0.8 V, and the charge overpotential is significantly reduced to 0.8 V. After 100 cycles, the capacity retention rate is as high as 95.3%. Its synergistic mechanism is mainly reflected in the potential complementarity of PTEO (3.8 V vs. Li + / Li) and PAQ (2.1V) form a continuous catalytic system, effectively widening the operating voltage window to 2.0-4.2V. Simultaneously, PTEO and PAQ form a complementary catalytic system, synergistically promoting the reversible formation and decomposition of Li2O2. Compared to single-modification systems and comparative examples, this invention, through the potential synergy achieved through molecular design, successfully overcomes the technical challenges of traditional lithium-oxygen batteries, which suffer from "high overpotential and low cycle life," boosting energy efficiency to 92.8%, demonstrating significant industrial application value.

[0060] (5) The Fe3O4@PPy@KB composite material prepared in Example 4 was drop-coated onto a glassy carbon electrode at a loading of 0.6 mg / cm2 and dried for use in rotating disk electrode (RDE) testing. The test conditions were: the electrolyte was 0.1 mol / L KOH saturated with O2, the rotation rates were set at 400, 900, 1600, and 2500 rpm, the potential scan range was 0.2–0.8 V (vs. RHE), and the scan rate was 10 mV·s. -1 The test results show that the limiting current density of the composite material of the present invention at 1600 rpm is 5.1 mA / mg, and the onset potential is 0.87 V (vs. RHE), while the onset potential of the control sample without the introduction of Fe3O4 and pore structure is 0.81 V and the limiting current density is only 3.4 mA / mg. The oxygen diffusion coefficient obtained by fitting the Levich equation is 2.36×10 -5 cm 2 ·s -1 , which is significantly higher than the 1.57×10 -5 cm 2 ·s -1 The improvement was about 50%. The results verified the significant role of the hierarchical pore catalytic system constructed by the synergistic construction of polymers and transition metals in enhancing the oxygen reduction reaction (ORR). It has good gas diffusion and electrocatalytic performance and is suitable for gas electrode systems such as lithium-oxygen batteries.

[0061] The present invention has verified its technical effects through various embodiments, including low-potential catalysis (PTEO decomposes Li2O2 at 3.7V), high-capacity output (the discharge capacity of the PAQ-modified electrode is increased by 50%), and long cycle life. The technical solution is both universal and scalable, and is suitable for various systems such as Li-O2 / CO2, Na-O2 / CO2, K-O2 / CO2, and lithium-sulfur batteries, providing an innovative solution for the commercialization of high-energy-density batteries.

[0062] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. A polymer mediator catalyst, characterized in that: The polymer mediator catalyst is an organic small molecule monomer with redox activity prepared by chemical or electrochemical polymerization.

2. The polymer-mediated catalyst according to claim 1, characterized in that The polymerization method of the polymer mediator catalyst is in situ or ex situ polymerization, and the organic small molecule monomer is selected from the redox mediator of metal-air battery or lithium sulfur battery, which is one or more of organic small molecule nitride, organic small molecule sulfide, quinone, and heteropoly acid.

3. Use of the polymer mediator catalyst according to claim 1 in preparing a cathode material for a rechargeable metal-air battery or a lithium-sulfur battery.

4. A composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery, characterized in that: The invention is composed of the polymer mediator catalyst according to claim 1, a carbon material and a binder.

5. The composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery according to claim 4, characterized in that: The mass ratio of the polymer mediator catalyst, carbon material and binder is (20-30): (55-70): (8-12).

6. The composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery according to claim 4, characterized in that: The carbon material is one or more of multi-walled / single-arm carbon nanotubes, carbon nanofibers, graphene, acetylene black, Ketjen black, Super P, ordinary carbon black, conductive graphite, biowaste-derived carbon, metal-organic framework-derived carbon, carbon-based composite materials or biochar materials.

7. The composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery according to claim 4, characterized in that: The metal-air battery is one of a Li-O2 / CO2 battery, a Na-O2 / CO2 battery, a K-O2 / CO2 battery, a Mg-O2 / CO2 battery or a Zn-O2 / CO2 battery.

8. The composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery according to claim 4, characterized in that: The composite positive electrode material has a multi-level pore structure, including micropores, mesopores and macropores, and the pore diameter is 0.5-200nm.

9. The composite cathode material for a rechargeable metal-air battery or lithium-sulfur battery according to claim 4, characterized in that: The composite positive electrode material further comprises transition metal nanoparticles, wherein the transition metal is selected from one or more of Fe, Co, Ni and Mn.

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